Liquid Sheet Chemistry Past Paper PDF

Liquid sheet 1. The vapour pressure of carbon disulfide, CS2, is 0.526 at 301 K. What is the vapour pressure of CS2 at 273 K? The enthalpy of vaporization of CS2 over this temperature range is 27.6 KJ/mol. [P = 0.17 atm] 2. The atmospheric pressure decreases with height. T...

Liquid sheet 1. The vapour pressure of carbon disulfide, CS2, is 0.526 at 301 K. What is the vapour pressure of CS2 at 273 K? The enthalpy of vaporization of CS2 over this temperature range is 27.6 KJ/mol. [P = 0.17 atm] 2. The atmospheric pressure decreases with height. The pressure at a height (h) above sea level = 4000m is given approximately by the barometric formula: P = P0 e −Mgh/RT , in which M=0.0289 kg. mol-1, g = 9.81 ms-2 and P0 is the atmospheric pressure. Assume that the enthalpy of vaporization of water is ∆Hvap = 40.6 kJ mol-1 , predict at what temperature water will boil at this height. (t= 86.85 oC) 3. It is desired to produce superheated steam at 120 ̊C. Under what pressure must water be boiled to achieve this? Normal boiling point of water = 100 ̊ C. Latent heat vaporization of water = 39.70 KJ/mol-1. [P = 1.91 atm] 4. The enthalpy of vaporization of benzene, C6H6 (l), is 33.9 KJ mol-1 at 298 K. How many liters of C6H6 (g), measured at 298 K and 95.1 mmHg, are formed when 1.54 KJ is absorbed by C6H6 (l) at a constant temperature of 298 K? [ V = 8.866 L] 1  5. The normal boiling point of chloroform (CHCl3) is 334 K. At 328 K, the vapour pressure of chloroform is 0.824 atm. What is the enthalpy of vaporization of chloroform for this temperature range? Also calculate the amount of heat required to evaporate 12 gm of CHCl3. [∆H = 29353.667 J/mole, q = 2947.65 J] 6. Benzaldehyde has a normal boiling point of 179 ̊C and a critical point at 422 ̊C and 45.9 atm. Estimate its vapor pressure at 100 ̊C? [P = 0.0987 atm] According to the phase diagram given for Compound Y, what description is correct? a) At 0oC and 1200 torr, Y exists as a solid. b) At the pressure and temperature of point 1, Y(s) will spontaneously convert to Y(g) and no Y(l) is possible. c) At the pressure and temperature at point 3, Y(s) Y(g). d) At the temperature and pressure at point 2, Y(l) Y(g) e) At the temperature and pressure at point 4, Y(g) will spontaneously convert to Y(l). 2  Curves of phase diagram represent equilibrium between…….. a) two phases b) three phases c) four phases d) None of the above answers Triple point in phase diagram represents equilibrium between ………. a) 2 states b) 2 phases c) 3 states d) 3 phases Draw a phase diagram for (Kr). The triple point (-169 ℃ and 0.175 atm), the normal melting point (-156 ℃), and critical point (-63 ℃ and 54.2 atm). 3  Then predict: 1. Which one is denser liquid or solid? Why? 2. Does the freezing point curve slant to left or right? 3. What is the effect of increasing pressure on freezing point? 4. What is the effect of increasing pressure on (Kr) solid? 5. What are the states that (Kr) can exist by increasing temperature at 1 atm? 4  Helium is the only known substance that has two different liquid phases called helium Ⅰ and helium Ⅱ as shown in its phase diagram. 2 1 1. What is the maximum temperature at which helium Ⅱ can exist? 2. What is the minimum pressure at which solid helium can exist? 3. What is the normal boiling point of helium Ⅰ? 4. Can solid helium sublimate? 5. How many triple points are there? 6. What are the phases and states which coexist at each triple point? 7. What is the name of point Z and how many phases and states at this point? 8. How can you obtain solid from liquid helium Ⅰ? 5